This invention relates generally to potato products and more particularly to par-fried potato products prepared for finish-frying at a later time.
Fried potato products, and french fries in particular, have been extremely popular over the last few decades. While it is generally agreed that fried potato products are best when freshly prepared from whole potatoes, the preparation of these products from whole potatoes is too time-consuming and costly for most restaurants and home consumers to undertake often. Therefore, most restaurants buy frozen french fries, which have been previously par-fried, and finish-fry them immediately prior to serving. Home consumers often buy frozen french fries and then oven bake or pan fry them prior to serving. Nevertheless, deep-fry or pan-fry finishing almost always results in a more flavorful, better-textured product than oven-bake finishing.
While most frozen french fries presently on the market result in reasonably satisfactory products when finish-fried, even the best presently available frozen french fries have flavor and texture defects. One defect results from the necessary dehydration of the par-fried potato product to between 23 and 26% moisture prior to freezing. This dehydration results in an increased uptake of oil during finish frying in comparison to freshly fried potatoes.
Furthermore, this moisture reduction often results in a final product that is leathery and tough. Texture is extremely critical to consumer acceptance of a food product, and especially consumer acceptance of french fries. Ideally, french fries should have a thin, golden, crispy skin and a meaty, but delicate, interior similar to that of a baked potato. Even if a previously frozen french fry appears and tastes similar to the fresh product, a tough or otherwise improper texture significantly decreases consumer acceptance.
Also, many persons are attempting to cutdown on their intake of dietary fats, especially saturated and polyunsaturated fats. Excessive intake of saturated fats can result in high cholesterol levels and an increased risk of heart attack. Excessive intake of polyunsaturated fats are suspected to increase the risk of cancer. French fries are typically fried in either saturated (from animal fat, peanut oil, hydrogenated vegetable oils, etc.) or polyunsaturated (corn oil, sunflower oil, etc.) fats. Thus, the increased fat absorption during finish frying exhibited by frozen french fries increases the health risks associated with these products, as well as increasing the caloric content of the final product.
Additionally, freezing, even quick freezing, results in structural damage due to ice crystal formation. This structural damage can decrease shelf-life, harm texture, and adversely affect taste.
Frozen french fries must be either thawed prior to finish frying or finish fried from the frozen state. Obviously, the threat of increased bacterial growth and time considerations make thawing prior to finish frying impractical. Also, frozen fries thawed prior to frying have an increased oil uptake. The use of frozen french fries in the finish frying step, however, obviously increases the time required for finishing and requires greater energy consumption to compensate for the temperature drop in the bath resulting from the introduction of the frozen fries. Further, ice crystals clinging to the outside of the french fries result in splattering, foaming, oxidation and bubbling of the frying oil.
To overcome these difficulties encountered with frozen fried potato products, attempts have been made to prepare par-fried potato products suitable for refrigeration. Nevertheless, for several reasons, these attempts have not achieved complete success and an acceptable, refrigerated par-fried potato product had not, to date, been produced.
A major problem with refrigerated products has been spoilage. The fat in french fries is highly susceptible to both reactions with oxygen and hydrolysis by moisture present within the fry. While hydrolysis from moisture within the french fry may be overcome to some extent by the incorporation of antioxidants such as ascorbic acid or erythorbic acid, oxidation by reaction with oxygen is more problematic.
One approach to preventing oxidation of food by reaction with oxygen has been vacuum packing. A major difficulty with this approach has been "weeping", i.e., the seepage of moisture from the inside of the product to its outer surface, which reduces the shelf-life of the product.
Another approach has been packing under carbon dioxide. However, when refrigerated fries are packed under carbon dioxide, carboxylic acid is formed, giving the product a tinny taste.
Par-fried french fries packaged under pure nitrogen do not develop carboxylic acids, but nitrogen exhibits no antimicrobial effects. Thus, par-fried products packed under nitrogen (or other inert gases) develop a stale taste rather quickly. This stale taste is believed to be a result of bacterial or mold growth.
The difficulty of storing par-fried potatoes at refrigeration temperatures has been noted in several studies. In one study, a taste panel scored french fries that had been finish-fried in deep fat after 3 days storage at 55.degree. F. significantly lower than french fries that had been held at 0.degree. F. Microbiological counts were also found to increase rapidly under such conditions (see O. Smith, Potatoes: Production, Storage, Processing, AVI Publishing Co. (1977), incorporated herein by reference, at pp. 340-373).
Also, the cost of maintaining products in the frozen state as opposed to refrigeration is high. Moreover, most industrial users of par-fried potatoes have more space available for refrigeration than freezing.